Updated

Officials say a contractor who was trying to turn off an alarm and hit the wrong switch caused the 90-minute outage of the 911 system in the nation's capital.

Alan Etter, spokesman for the Office of Unified Communications, tells media outlets on Monday that the contractor's mistake shut down the 911 system between 11 p.m. Saturday and 1 a.m. Sunday.

Officials say the contractor has been banned from all District buildings.

Chris Geldart is director of the city's Homeland Security and Emergency Management Agency. He says the loss of power prevented calls from being transferred to a backup center.